PROJECT ABSTRACT The objective of this research is to improve treatment for adults with depression and comorbid cannabis use disorders (CUD) with an innovative, social media-assisted intervention strategy. The proposed intervention combines peer and therapist social network support via Facebook with an integrated, computer-assisted therapy program combining cognitive behavioral therapy (CBT) and motivational enhancement therapy (MET) to reduce cannabis use and depressive symptoms. In 2014 the applicant received a NIDA High Priority, Short- Term Project Award to pilot test SHADE (Self-Help for Alcohol and Other Drug Use and Depression), a computerized intervention combining CBT and MET, in a primary psychiatric care setting, where integrated interventions addressing both mental health and substance use disorders (SUDs) are not readily accessible. Preliminary data indicate that integrating SHADE with psychiatric care for depression: (a) is feasible and acceptable, (b) facilitates treatment engagement and retention in a difficult-to-treat comorbid population with major depression and CUD; and (c) produces significant reductions in depressive symptoms and cannabis use. To optimize this model of evidence-based psychotherapy implementation for depressed cannabis users receiving usual care (TAU) in a primary psychiatric setting, the proposed study integrates a social network support component into the SHADE intervention program. The specific aims of this research are: 1) To develop, with user feedback, a social media-assisted intervention (Connected Cannabis Users? Network for Enhancement of Cognitive Therapy; CONNECT) for depressed cannabis users that combines SHADE with peer and therapist social network support via a private Facebook group for reducing cannabis use and depression, and improving treatment retention; 2) To test, in a pilot RCT (N=50), the incremental efficacy of CONNECT over and above SHADE in improving cannabis use, depression, and healthcare outcomes among depressed adults with CUD in a primary psychiatric setting; 3) To examine whether social network variables moderate or mediate the impact of CONNECT. We hypothesize that SHADE + CONNECT will yield superior clinical outcomes relative to SHADE in reducing cannabis use, improving depressive symptoms and treatment retention, and reducing health service utilization during and after treatment. Moreover, we expect that the social network support component of CONNECT will have a direct effect on the quality and quantity of participants? social support network for addiction and depression recovery, a recognized mechanism of change in CBT and MET approaches to the treatment of comorbid populations, and these changes will be associated with cannabis use and depression outcomes. By providing both clinician and peer support to maximize skills acquisition from SHADE, CONNECT may provide a cost-effective and easily deployable strategy for the treatment of depressed cannabis users in a primary psychiatric care setting, a model that may be extended to other settings where SUDs are undertreated.